This invention relates to a circuit for use in displaying a facsimile or a like image signal on a display unit, such as a CRT display.
As will later be described in detail, a frame factory is used on displaying an image signal on a display unit. The frame memory is for storing picture elements of the image signal. The picture elements are read from the frame memory for display on the display unit at a display clock rate of the display unit. It is usual on displaying the image signal to extract predetermined elements of the picture elements read from the frame memory. When the predetermined elements are, for example, 4/25 in number of the picture elements and should be displayed at the display clock rate of 20 MHz, the frame memory must be read at as high a reading rate as 125 MHz. This high reading rate is impractical. Furthermore, the frame memory is in use throughout during display of the image signal.